The U.S. and representatives of the European Union have agreed to impose joint sanctions against Iran in January and are considering breaking off talks with the country, as patience with Tehran’s nuclear activities wears thin, according to people familiar with the matter.

Western officials are discussing making further talks with Iran contingent on Tehran’s progress toward compliance with existing United Nations Security Council resolutions, which call on Iran to cooperate fully with the International Atomic Energy Agency, the U.N.’s nuclear watchdog.

Iran returned to the negotiating table this month in Geneva with the five permanent members of the U.N. Security Council plus Germany, which seek to contain Tehran’s nuclear program. The talks led to an agreement to another round of discussions early next year in Istanbul.